A cross-sectional epidemiological study on prevalence of hearing loss was carried out in an age- and Down's syndrome- stratified random sample of 1598 persons drawn from a base population of 9012 persons, representative of the Dutch adult population of intellectual disability (ID) service users. The re-weighted population prevalence is 30.3% (95% confidence interval [CI]: 27.7-33.0%). Subgroup prevalences range from 7.5% (95% confidence interval [CI]: 3.6-13.3) in the subgroup aged 18-30 years with ID by other causes than Down's syndrome, up to 100% (95% CI: 79.4-100%) in adults over 60 years of age with Down's syndrome. Down's syndrome (OR 5.18, 95% CI 3.80-7.07) and age were confirmed to be risk factors. Age-related increase in prevalence in persons with Down's syndrome appears to occur approximately three decades earlier, and in persons with ID by other causes approximately one decade earlier than in the general population.